samurai's compassion; warrior's mercy
Refers to the mercy or compassion shown by a samurai, often implying a noble, dignified leniency toward a defeated or weaker opponent. A set phrase evoking traditional bushido values.
Show a samurai's mercy to the enemy.
That is exactly what is called a samurai's compassion.
A set phrase combining 武士 (samurai) and 情け (compassion/mercy). The exact historical origin is uncertain, but it reflects the bushido ideal of showing mercy to a defeated opponent.